Well packing apparatus



y 28, 1968 D E. YOUNG 3,385,365

v WELL PACKINGv APPARATUS Filed May 17. 1966 3 Sheets-Sheet 1 .50 we 5 Val/fig LVVENTOR y 1968 D. E. YOUNG 3,385,365

WELL PACKING APPARATUS Filed y 17. 1966 3 Sheets-Sheet 3 %46' 6/ 25 .Da wa 1 ou/7 INVENTOR BY; A I

drrokva United States Patent "ice 3,385,365 WELL PACKING APPARATUS David E. Young, Bellaire, Tex., assignor to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed May 17, 1966, Ser. No. 550,706 12 Claims. (Cl. 166-120) This invention relates to apparatus for packing-off a well bore; and, more particularly, to packing apparatus which can be set in a Well with predetermined anchoring and sealing forces and, once set, is responsive to pressure differentials acting from either direction in the well bore to immediately develop, when needed, increased forces proportionately related to the acting pressure that are sufficient to secure the apparatus in place and sealingly engaged.

In conducting such well-completion operations as acidizing, cementing, or fracturing, a full-opening well packer dependently coupled from a tubing string is positioned at a particular depth in a cased well and the packer set to isolate the formation interval to be treated from the remainder of the well bore thereabove. Treating fluids are then pumped downwardly at high pressures through the tubing and packer and introduced into the formation being treated through perforations appropriately located in the casing.

In those instances where a well having several producing formations is being completed, a selectively operable bridge plug is usually dependently coupled beneath the full-opening packer. Such a bridge plug permits intervals of selected length to be packed-off for selective treatment of different formation zones with only a single trip into the well. It will be appreciated that, during the course of such completion operations, these packing apparatus are usually subjected to high fluid pressures acting alternately from both above and below them. Thus, these packers and bridge plugs must be firmly sealed and securely anchored against pressure differentials acting in either longitudinal direction.

Heretofore, extendible slip members have typically been employed to secure such packing apparatus from movement in at least one direction. Extendible anchoring members have also been developed which are hydraulically actuated by pressures acting from at least one direction for securing the apparatus against shifting in that direction. Such extendible members, however, generally employ toothed members that must be embedded into the casing to secure the apparatus. Aside from damaging the casing, such toothed members are generally effective against movement in only one direction so that two oppositely directed sets of these members are usually employed to prevent shifting of the apparatus in either direction. Moreover, once a toothed member is embedded, it will be even more tightly embedded by subsequent loads and, thereby, Complicate its extrication as well as further damage the casing.

Accordingly, it is an object of the present invention to provide new and improved well-packing apparatus having hydraulic means for setting and maintaining packing means and anchoring means engaged with predetermined forces and which, should a pressure differential require additional sealing or anchoring forces, will respond immediately to develop still greater forces that are proportionately related to the pressure differential acting across the packing apparatus.

This and other objects of the present invention are obtained by providing packing apparatus with first hydraulic means for initially urging one or more wall-engaging means against the casing with a first force by applying predetermined loads through the tubing string and second hydraulic means for responding to a pressure differential 3,385,365 Patented May 28, 1968 otherwise sufiicient to shift the apparatus to immediately further urge the wall-engaging means with an increased force proportionately related to this differential.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and eiample of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view of a full-bore packer and a bridge plug employing principles of the present invention and depicted as they would appear within a well bore;

FIGS. 2A2C are detailed, successive cross-sectional views of the bridge plug of FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 33 of FIG. 2B; and

FIGS. 4A-4C are views similar to FIGS. 2A2C but showing the bridge plug in its set position.

In general, the retrievable bridge plug 10 of the present invention is comprised of an actuating body or mandrel 11 that is telescoped within a tubular housing 12 and selectively movable therein between an elevated neutral or inactive position (FIG. 2) and a lower operative position (FIG. 4), in which latter position the mandrel is free to shift a limited distance either upwardly or downwardly relative to the housing. Pressure-developing means 13 are included which, as the mandrel 11 is shifted into its operative position relative to the housing 12, develop a hydraulic pressure suflicient to expand pressure-responsive packing means 14 and anchoring means 15 outwardly into firm engagement with an adjacent wall in a well bore. Selectively operable hydraulic means 16 are also provided for maintaining sufficient hydraulic pressure on the wallengaging means 14 and 15 to insure that the packing means remain sealingly engaged and the anchoring means secures the bridge plug 10 against well bore pressure differentials until the mandrel is returned to its inactive position.

Since those skilled in the art Will recognize that such a well tool is typically comprised of separate tubular elements threadedly connected to one another to facilitate its manufacture and assembly, the drawings have been somewhat simplified by showing some of these separate elements as a single member for purposes of greater clarity.

Turning now to FIG. 1, a typical full-bore packer 17 is shown dependently connected to a tubing string 18 and positioned within a well bore 19 having a casing 20 set therein. The retrievable bridge plug 10 of the present invention is releasably coupled by a fishing neck 21 to an overshot 22 dependently connected beneath the packer 17.

Matched J-slots 23 (FIG. 2A) are arranged on opposite sides of the fishing neck 21 to cooperatively receive inwardly projecting lugs 24 on the overshot 22 whenever it is lowered over the fishing neck. After the lugs 24 have entered the open upper end of the long portions of the I-slot 23, the lugs are lockingly engaged in the closed short portion of the J-slots by a concerted application of counter-clockwise torque and a slight upward pull on the tubing string 18. Conversely, the overshot 22 is selectively disengaged from the fishing neck 21 by lowering the tubing string 13 slightly, torquing it to the right and then pulling upwardly. By employing such a releasable coupling, the bridge plug 10 can be set at the lower limit of a particular formation interval and the packer 17 uncoupled and subsequently set thereabove irrespective of the length of the tubing subconnecting them.

For providing bypass means around the packing means 14, fluid communication through the axial bore 25 of the mandrel 11 is selectively controlled by an annular valve member 26 which is slidably disposed around the upper end of the mandrel over lateral bypass ports 27 therein and fluidly sealed thereto by O-rings 28 and 29 straddling the bypass ports. Lateral ports 30 in the slidable valve member 26 are appropriately arranged to register with the bypass ports 27 whenever the valve member is in the position illustrated in FIG. 2A. The slidable valve member 26 is arranged to be shifted longitudinally by the overshot 22 so that the ports 27 and 30 are brought into register when the overshot is engaged over the fishing neck 23 (FIG. 2A) and the bypass ports 27 are covered by the valve member whenever the overshot is removed (FIG. 4A). The lower end of the mandrel bore 25 is, of course, always open.

Whenever the overshot 22 is being removed, a group of dependent resilient fingers 31 spaced around the lower portion of the overshot have inwardly projecting shoulders 32 that engage a shoulder 33 on the sliding valve member 26 to pull it upwardly and close the bypass ports 27. As the valve member 26 is pulled upwardly, depending resilient fingers 34 around the lower end of the valve member are cammed outwardly as they pass over an annular shoulder 35 around the mandrel 11. After clearing this mandrel shoulder 35, the lower end of these fingers 34 then engage the upper end of this shoulder to hold the slidable member 26 in its uppermost or portclosed position (FIG. 4A) after the overshot 22 has been removed. A shoulder 36 projecting inwardly from the central portion of the overshot 22 engages the valve member 26 and shifts it downwardly to its open position (FIG. 2A) whenever the overshot is being coupled to the fishing neck 21.

As seen in FIG. 2B, the pressure-responsive packing means 14 include a slidable sleeve member 37 having an outwardly enlarged upper end 38 and an outwardly enlarged lower end 39 that is telescopically fitted within the upper portion of the tubular housing 12 and fluidly sealed thereto by an O-ring 40 below an inwardly projecting housing shoulder 41. A shorter slidable sleeve member 42 is telescopically arranged around the central portion of the other setting sleeve 37. This shorter sleeve member 42 has a lower end 43 extending into the housing 12 above the housing shoulder 41 and an outwardly projecting enlarged upper end 44 that is normally shouldered on the upper end of the housing and fluidly sealed to the inner sleeve 37 by an O-ring 45. An O-ring 46 in the upper end of the housing 12 fluidly seals the shorter outer setting sleeve to the housing and defines an enclosed space 47 between the setting sleeves 37 and 42 and the other O-rings 4t) and 45. An elongated external spline 48 extending longitudinally along the inner setting sleeve 37 is cooperatively received within complementarily internal grooves in the housing shoulder 41 and lower end 43 of the outer sleeve 42 to co-rotatively secure these three numbers to one another and limit their relative movement to longitudinal telescopic travel.

Elastomeric packing means 14, such as a plurality of stacked annular elements 49 mounted around the exposed portion of the inner sleeve, are arranged between the outwardly directed enlarged upper ends 38 and 44 of the sleeves 37 and 42 to be foreshortened thereby and expanded outwardly whenever the setting sleeves are relatively telescoped together. Conversely, longitudinal movement in the opposite direction of the sleeve ends 38 and 44 as the setting sleeves 37 and 42 expand allow the packing rings 49 to relax and return to their normal position.

Thus, it will be appreciated that, upon application of suflicient hydraulic pressure in the enclosed space 47, the setting sleeves 37 and 42 will be telescoped. As the setting sleeves 37 and 42 contract, the elastomeric elements 49 will be foreshortened and expanded radially outwardly against the casing wall. By appropriately selecting elements having particular elasticity and dimensions suitable for a given range of casing diameters, it can be readily determined that, for a given hydraulic pressure in the enclosed space 47, the elements 49 will be urged against the casing 20 with a force proportionately related to this hydraulic pressure. Accordingly, those skilled in the art will understand that by applying at least a predetermined hydraulic pressure in the enclosed space 47, the elastomeric elements 49 will be sealingly engaged against the casing 20 with a force sufficient to withstand well bore pressure differentials up to a particular magnitude.

Mounted around the central portion of the housing 12 is the hydraulically actuated, radially expansible anchor 15, with portions thereof being shown in cross-section in FIG. 3. This anchor 15 includes an extensible elastomeric sleeve 50 encircling the central portion of the housing 12 with a plurality of elongated wall-engaging members 51 and 52 being longitudinally mounted uniformly around the periphery of the sleeve. The enlarged upper and lower ends 53 and 54 of the elastomeric sleeve 50 are secured by slidable annular retainers 55 and 56 within opposed peripheral recesses 57 and 58 around the housing 12. O-rings 59 and 60 around the retainers 55 and 56 fluidly seal the sleeve ends 53 and 54 within the recesses 57 and 58 to provide a fluid-tight space 61 between the sleeve 50 and housing 12.

Each of the casing-engaging members 51 and 52 is elongated and has a thick, arcuate cross-section (FIG. 3). Alternate ones of the casing-engaging members 51 are centrally aligned and mounted on the outer convex surface of relatively thin, elongated, arcuate backing members 62 (FIG. 3). A sufficient number of these mounted members 51 are disposed around the periphery of the clastomeric sleeve 50 that the backing members 62 substantially encompass the sleeve. The remaining casing-engaging members 52 are unmounted and alternately disposed between the mounted casing-engaging members 51 in such a manner that the unmounted members 52 straddle adjacent backing members 62 and cover the gaps 63 therebetween.

The ends of the casing-engaging members 51 and 52 are beveled, as at 64 (FIG. 2C), for reception within the opposed annular housing recesses '57 and 58. It will be appreciated that, although the casing-engaging members 51 and 52 will move radially outwardly whenever the elastomeric sleeve 50 is inflated, the beveled ends 64 of the casing-engaging members cannot escape from the housing recesses 57 and 58.

By applying hydraulic pressure within the fluid-tight space 61, the casing-engaging members 51 and 52 will be urged against the casing 20 with a force proportionately related to this pressure. Thus, by appropriately selecting the materials and contact surface areas for the casingengaging members 51 and 52, it can be readily determined that a particular hydraulic pressure in the fluidtight space 61 will secure the bridge plug 10 against longitudinal shifting by pressure differentials in the well up to a particular magnitude.

To secure the housing 12 so that the mandrel 11 may be moved relative thereto from its inactive or neutral position (FIG. 2) to its operative position (FIG. 4), typically arranged drag blocks 65 (FIG. 2C) are mounted around the lower portion of the housing. Compression springs 66 normally urge the drag blocks 65 against the casing 20 with sufiicient force to permit the mandrel 11 to be moved relative to the housing 12 but without unduly hampering movement of the bridge plug 10 as it is being positioned in the well bore 19.

Turning now to the pressure-developing means 13 and 16 for the bridge plug 10, the housing 12 is arranged in such a manner as to provide an annular chamber 67 (FIG. 2B) above the upper end of the anchor 15. A similar annular chamber 68 (FIG. 2C) is also formed below the lower end of the anchor 15. An annular clearance space 69 (FIGS. 2B-2C) between the mandrel 11 and housing 12 provides fluid communication between the upper and lower chambers 67 and 68. A plurality of radial ports 70 through the housing 12 adjacent to the elastomeric sleeve 50 provide fluid communication from this annular'clearance space 69 into the sealed space 61 underneath the elastomeric sleeve.

Longitudinal passages 71 and 72 through the housing 12 provide fluid communication from the lower portion of the up er annular chamber 67 to the enclosed space 47 between the setting sleeves 37 and 42. Although the e longitudinal passages 71 and 72 could just as well be formed within the housing 12 itself, to facilitate the fabrication and assembly of the bridge plug 10, these passages are provided by disposing telescoped inserts 73 and 74 in the housing 12 between appropriately arranged shoulders, as at 41, 75 and 76 therein and fluidly sealing them to one another by an O-ring 77.

Extending upwardly from the upper annular chamber 67 is an annular space 78 between the exterior of the mandrel 11 and the interior of the inner setting sleeve 37. A pair of spaced O-rings 79 within the enlarged upper end 38 of the inner setting sleeve 37 straddle a lateral filling port 80 through the upper end of this sleeve. By slightly reducing the external diameter of the mandrel 11 at a suitable posizion, as at 81, fluid communication is provided from the exterior of the bridge plug to the annular space 78 so long as the mandrel 11 is held in its inactive or neutral position as depicted in FIG. 2.

By leaving the filling port 80 open whenever the bridge plug 10 is within a well bore, should the bridge plug move into a slightly smaller casing diameter, the resulting retraction of the anchor will not increase the pressure in the hydraulic system since the fluid therein will be exhausted through the lateral port. Similarly, as the bridge plug 10 moves into a larger size of casing, well fluids can refill the hydraulic system through the port 80. Once, however, the mandrel 11 is moved from its neutral position to its active position, the sealing engagement of the O-rings 79 around the mandrel will prevent further discharge of fluid within the hydraulic system through the lateral port 80.

A lateral port 82 is also arranged through the mandrel 11 so that when the mandrel is in its neutral position (FIG. 2), the port will be above the uppermost of the O-rings 79. Whenever the mandrel 11 is shifted into is active position (FIG. 4), the lateral port 82 will be below the O-rings 79 and provide fluid communication from the axial bore of the mandrel of the annular space 78 to keep the annular space filled.

Turning now to the hydraulic means 13 and 16, the upper end of the upper annular chamber 67 and the lower end to the lower annular chamber 68 are respectively closed by annular piston members 83 and 84 which are slidably mounted therein relative to both the mandrel 11 and housing 12. The upper slidable piston member 83 (FIG. 2B) is adapted for engagement by a downwardly directed mandrel shoulder 85 that is a short distance thereabove whenever the mandrel 11 is in its inactive position. Annular grooves around the outer and inner surfaces, respectively, of the upper piston member receive sealing members 86 and 87 which fluidly seal the slidable piston member 83 relative to the mandrel 11 as well as to the housing 12. To provide fluid communication between the upper chamber 67 and annular space 78 whenever the mandrel 11 is in its inactive or neutral position, bypass means are arranged around the upper piston member 83 such as a longitudinal groove 88 in the outer surface of the mandrel and just below the mandrel shoulder 85. Although the inner sealing member 87 within the upper piston could be an O-ring, it is preferred to employ a sealing ring that protrudes slightly above the upper face of the piston 83. In this manner, there is no frictional engagement of the mandrel 11 with the piston 83. To seal, the sealing member 87 will also engage the lower face of the mandrel shoulder 85 rather than only around the perimeter of the mandrel 11 itself.

The lower slidable piston member 84 (FIG. 2C) is biased downwardly by a spring 89 so that the lower piston normally rests against an upwardly directed shoulder 90 formed in the housing 12 below the lower chamber 68.

Internal and external annular grooves around the piston receive O-rings 91 and 92 to fluidly seal the slidable piston member 84 relative to the mandrel 11 and the housing 12. To compensate for any misalignments between any one or all of the mandrels 11, housing 12 and lower piston, the piston 84 is preferably made in two portions as shown loosely secured together by a transverse pin 93.

Mounted in an inwardly opening recess 94 in the lower piston member 84 is an expansible split-nut 95 having teeth adapted for cooperative engagement with upwardly directed teeth 96 on the mandrel 11 when it is in its operative position (FIG. 4). When the mandrel 11 is in this operative position, the teeth 96 are free to ratchet further downwardly through the nut 95 on the lower piston 84. Upward movement of the mandrel 11 will, however, co-engage the teeth 96 with the nut 95 and shift the lower piston 84 upwardly.

To releasably secure the mandrel 11 in its inactive or neutral position, a second expansible split-nut 97 is loosely disposed within an inwardly opening recess 98 around the lower portion of the housing 12 and adapted for cooperative engagement with downwardly facing teeth 99 on the lower end of the mandrel. By appropriately arranging the teeth 99 and those in the lower split-nut, the mandrel 11 must be first rotated to unthread it from the expansible split-nut 97 before it can be moved downwardly. To return the mandrel 11 to its inactive or neutral position, however, it is necessary only to rotate it sufficiently to disengage the threads 99 from the split-nut 97. Then, when the mandrel 11 is pulled upwardly relative to the housing 12, the lower teeth 99 will ratchet through the expansible split-nut 97. An inwardly projecting housing shoulder 100 (FIG. 2B) is suitably arranged to engage the upper end of the mandrel shoulder and prevent further upward movement of the mandrel 11.

Accordingly, it will be recognized that so long as the teeth 99 are engaged with the lower split-nut 97, the mandrel 11 cannot move downwardly relative to the housing 12. With the mandrel 11 in this neutral position (FIG. 2), the hydraulic pressure in the liquid-filled chamber 67 and 68 and spaces 47, 61 and 78 will be equal to the pressure of the fiuids in the well bore 19 exterior of the bridge plug 10. To release the mandrel 11 from its neutral position, it is necessary only to rotate the mandrel a sufiicient number of turns in the appropriate direetion to disengage the mandrel threads 99 from the lower split-nut 97. The frictional restraint of the drag blocks 65 with the casing 20 will, of course, secure the housing 12 sufficiently for the mandrel 11 to be rotated relative thereto.

Once the mandrel threads 99 have been disengaged from the lower split-nut 97, the mandrel is free to shift longitudinally. As the mandrel is shifted downwardly, the upper mandrel threads 96 will ratchet into the upper split-nut 95 on the lower piston member 84. At about t is point, the mandrel groove 88 will pass below the sealing member 87 which will then be fluidly sealed to the mandrel 11 as the shoulder 85 thereon engages the upper face of the annular piston member 83 and the sealing member.

Once the sealing member 87 is fluidly sealed to the mandrel 11, further downward movement of the mandrel shoulder 85 will shift the upper piston member downwardly to develop a uniform pressure throughout the hydraulic sysem that is related to the distance that the piston 83 is shifted. The housing shoulder will prevent downward movement of the lower piston 84. Thus, as previously described, whatever hydraulic pressure is developed will telescope the setting sleeve 37 and 42 together to expand the packing elements 49 as well as serve to force the casing-engaging members 51 and 52 outwardly against the casing 20.

Turning now to the operation of the bridge plug 10.

With the bridge plug 19 connected to the overshot 22, as shown, for example, in FIG. 1, it and the packer 17 are moved into position in the well bore 19. As the bridge plug 10 is being positionedyit will be appreciated that the ports 27 will be open so fluids in the well bore 19 can move freely through the mandrel bore 25 to bypass the packing means 14. Whenever the bridge plug 10 has been positioned at a desired depth into the well bore 19, the tubing string 18 is halted and slowly rotated.

Once the tubing string 18 has been rotated sufficiently to disengage the lower mandrel threads 99 from the lower split-nut 97, the mandrel 11 is free to be shifted downwardly relative to the housing 12. As the mandrel 11 is moved further downwardly, the sealing member 87 is first sealed with the mandrel and shoulder 85 and the upper piston 83 is then shifted downwardly once it is engaged by the shoulder. As the upper piston 83 is shifted downwardly, pressure will be developed in that portion of the now-sealed hydraulic system below the upper piston. The lower piston 34 is prevented from moving downwardly by the shoulder 90. As the mandrel 11 travels downwardly, the upper mandrel threads 96 will ratchet freely downwardly through the upper split-nut 95 until the mandrel is halted. Once the mandrel 11 is halted, however, it will be prevented from returning upwardly by the co-engagement of the upper mandrel threads 96 within the upper split-nut 95.

This developed hydraulic pressure is, of course, proportionately related to the downward force applied to the mandrel 11. Thus, by observing the weight indicator (not shown) that is typically used at the surface to measure the upward pull required to support the string of tubing and tools in the well bore at any given moment, it will be possible to slack-off a particular magnitude of weight on the tubing string 18 to develop a corresponding predetermined pressure in the hydraulic system for urging the wall-engaging means 14 and 15 against the casing with a predetermined force. This predetermined force is, of course, selected in accordance with the anticipated well conditions.

Once the mandrel 11 has reached the position shown in FIG. 4, the tubing string 18 is appropriately manipulated to remove the overshot 22 from the fishing neck 21. As the overshot 22 is removed, the valve member 26 is moved upwardly by the depending fingers 31 and blocks fluid communication through the mandrel bore 25 and bypass ports 27. Once the valve member 26 is closed, the bridge plug 10 is then securely anchored and tightly packed-off against the casing 20 and is capable of withstanding substantial pressure differentials acting in either direction from above or below the bridge plug.

It will be understood, of course, that well bore pressures can change during the course of a typical completion operation. Assuming, for example, that the pressure in the well bore 19 below the bridge plug 10 is greater than that above, the resulting pressure differential will be acting upwardly against the bridge plug. This pressure differential will therefore be acting against the transverse crosssectional area of the mandrel 11 through the uppermost O-rings 79. It will also be recognized that, in this instance, the effective pressure-developing area for the hydraulic system will be the annular cross-sectional area between the O-rings 86 and 92, i.e., the difference between the outside diameters of the lower and upper pistons 83 and 84. Although these effective areas can, of course, be varied, it is preferred to arrange the various elements so this pressure-developing area will be equal to the area of the mandrel 11 through the O-rings 79. In this manner, the hydraulic pressure that is developed will not be too excessive.

It will be understood, of course, that an upwardly acting pressure differential will not be effective to move the mandrel 11 and lower piston 84 upwardly until the differential exceeds the pressure previously developed in the hydraulic system upon setting of the bridge plug 10. Once this trapped hydraulic pressure is exceeded, however, the mandrel 11 and lower piston 84 will be immediately moved upwardly to develop a still greater pressure in the hydraulic system to urge the packing means 14 and anchoring means 15 more firmly against the casing 20. There will be no lost motion in the mandrel 11 and an immediate pressure increase will be obtained. Should this upward acting pressure differential diminish, the spring 89 will return the lower piston 84 and mandrel 11 downwardly. It will be recognized, of course, that the upper piston 83 will remain firmly engaged against the mandrel shoulder 85.

It should be noted in passing that (as shown in FIG. 4) when there is a pressure differential acting upwardly, the housing 12 will shift slightly upwardly until stopped by the lower ends of the easing-engaging members 51 and 52. This would leave a slight gap at the opposite ends of the casing-engaging members 51 and 52 through which the elastomeric sleeve could be extruded were it not for the upper slidable retainer 55. To prevent this extrusion, the slidable retainer 56 will be urged upwardly by the developed pressure and be firmly engaged against the lower ends of the casing-engaging members 51 and 52. When the pressure differential is acting downwardly, the same operation will occur. Should, perchance, there be a greater pressure above the bridge plug 10 than that below, the mandrel 11 will be urged further downwardly and, if necessary, the upper mandrel threads 96 are free to ratchet further downwardly through the upper nut 95. Here again, the mandrel 11 cannot be moved downwardly until the pressure forces acting on the mandrel are sufficient to exceed those acting upwardly thereon from the piston 83 to shoulder 85. However, before the hydraulic pressure in the system becomes inadequate to secure the bridge plug 10, a downwardly acting pressure differential otherwise tending to shift the bridge plug downwardly will be effective to develop a greater anchoring force.

It should be noted, however, that in this latter instance, the mandrel 11 and piston 84 will not be returned subsequently to their initial positions if the mandrel threads 96 are ratcheted into engagement with .one or more still lower threads in the upper split-nut 95. This poses no particular problem, however, since the bridge plug :10 will only be held with a greater sealing and anchoring force until released.

To retrieve the bridge plug 10, it is necessary only to re-engage the overshot 22 over the fishing neck 21. As the overshot 22 is being lowered over the fishing neck 21, the shoulder 36 on the overshot will engage the upper end of the slidablc valve member 26 to shift it downwardly to its initial position. Once the valve member 26 is shifted downwardly suflicient to again bring ports 27 and 30 into register, pressure will be equalized across the bridge plug 10. Then, by picking-up and rotating the tubing string 18 in an appropriate direction, the upper mandrel threads 96 will be disengaged from the upper splitnut 95.

Once these threads 96 have been disengaged, the mandrel 11 is again free and can be pulled upwardly by the tubing string 18. As the mandrel 11 shifts upwardly, the lower mandrel threads 99 will ratchet upwardly through the lower split-nut 97 to again secure the mandrel in its neutral position (FIG. 2). As the mandrel 11 returns upwardly, a shoulder 101 below the piston 83 picks up the upper piston. A shoulder 102 above the piston 83 will engage the top of the upper piston and prevent it from mOVing further upwardly as the reduced-diameter portion 88 on the mandrel 11 is again moved under the sealing member 87. This will, of course, release the pressure in the hydraulic system to permit retraction .of the packing means 14 and anchoring means 15.

It will be appreciated, therefore, that the present invention provides new and improved packing apparatus that can be securely anchored in a well against pressure differentials acting in either direction. By setting the packing apparatus 'with a predetermined force, it will remain fixed against anticipated pressure differentials. Should these difierentials increase, however, means are provided whereby additional anchoring forces will be developed as required to maintain the packing apparatus sealed and in position. Of particular importance, it will be appreciated that the releasably connected lower piston will permit the mandrel to be freely moved from an inactive position to an effective position but still be in position to develop additional hydraulic pressure where needed and without any lost motion of the mandrel.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A well tool sized and adapted for reception in a well bore comprising: first and second telescoping members movable relative to one another between spaced positions; pressure-responsive anchor means on said first member and adapted for extension into anchoring engagement with a wall in a well bore in response to an actuating pressure; pressure-chamber means fluidly coupled to said anchor means and including first and second pistons therein between said members; means responsive to movement of said second member from one of its said positions toward the other of its said positions for moving said first piston to develop an actuating pressure in said pressure-chamber means; and means releasably securing said second piston to said second member whenever said second member is in its said other position for developing a greater actuating pressure in said pressure-chamber means proportional to pressure diflerentials in the Well bore tending to return said second member to its said one position.

2. The well tool of claim 1 further including pressureresponsive normally-retracted packing means on said first member fluidly coupled to said pressure-chamber means and adapted for extension into sealing engagement with the well bore wall in response to an actuating pressure.

3. The well tool of claim 2 further including bypass means normally open to the exterior of said well tool for compensating for changes in the volume of said anchor and pressure-chamber means whenever said second member is in its said one position, and means responsive to movement of said second member toward its said other position for closing said bypass means to seal said pressure-chamber means.

4. A well tool sized and adapted for reception in a well bore comprising: first and second telescoping members movable relative to one another between spaced positions; pressure-responsive anchor means on said first member and adapted for extension into anchoring engagement with a wall in a well bore in response to an actuating pressure; pressure-chamber means fluidly coupled to said anchor means and including a piston therein between said members; bypass means normally open to the exterior of said well tool for compensating for changes in the volume of said anchor and pressure-chamber means whenever said second member is in one of its said positions; first means responsive to movement of said second member toward the other of its said positions for closing said bypass means to seal said pressure-chamber means; and second means responsive to movement of said second member toward its said other position for moving said piston to develop an actuating pressure in said pressurechamber means after said bypass means is closed.

5. The well tool of claim 4 further including pressureresponsive normally-retracted packing means on said first member fluidly coupled to said pressure-chamber means and adapted for extension into sealing engagement with the well bore wall in response to an actuating pressure.

6. A well tool sized and adapted for reception in a well bore comprising: a housing; normally-retracted wallengaging means on said housing and adapted for extension against a wall in a well bore in response to an actuating pressure; a body movably disposed in said housing, said body being adapted for releasable connection to a suspension member and movable thereby relative to said housing from a normal position to another position; first hydraulic means responsive to movement of said body toward said other position for developing an actuating pressure to extend said wall-engaging means against the well bore wall with a force proportionately related to the force applied to said body by a suspension member; and second hydraulic means releasably securable to said body whenever it is in its said other position and responsive to pressure differentials in the well bore tending to move said body from its said other position toward its said normal position for developing a greater actuating pressure to urge said wall-engaging means against the well bore wall with an increased force proportionately related to such a pressure differential.

7. The well tool of claim 6 wherein said second hydraulic means includes means defining an enclosed liquidreceiving space in said housing in fluid communication with said wall-engaging means, piston means in said enclosed space, and means releasably securing said piston means to said body for movement thereby toward its said normal position in response to such pressure differentials.

8. The well tool of claim 6 wherein said first hydraulic means includes means defining an enclosed liquid-receiving space in said housing in fluid communication with said wall-engaging means, piston means in said enclosed space. and means on said body for shifting said piston means into said enclosed space to develop an actuating pressure as said body is moved toward its said displaced positions.

9. The well tool of claim -8 wherein said second hydraulic means includes second piston means in said enclosed space, and means releasably securing said second piston means to said body for movement thereby toward its said normal position in response to such pressure differentials.

10. A well packer sized and adapted for reception in a well bore comprising: a tubular housing; normally-retracted anchoring means on said housing and adapted for extension against a wall in a well bore in response to an actuating pressure to secure said housing relative to the wall; normally-retracted packing means on said housing and adapted for extension into sealing engagement with the well bore wall in response to the actuating pressure; a body movably disposed in said housing, said body being adapted for releasable connection to a suspension member and longitudinally movable thereby relative to said housing from a normal position to successively more advanced longitudinally-displaced positions; first hydraulic means responsive to movement of said body toward said displaced positions for developing an actuating pressure to respectively extend said anchoring and packing means against the well bore wall with a force proportionately related to the force applied to said body by the suspension member; and second hydraulic means releasably securable to said body whenever it is in one of its said displaced positions and responsive to pressure differentials in the well bore tending to move said body from one of its said displaced positions toward its said normal position for developing a greater actuating pressure to respectively urge said anchoring and packing means against the well bore wall with an increased force proportionately related to such a pressure differential.

11. The well packer of claim 10 wherein said first hydraulic means includes means defining an enclosed liquid-receiving space in said housing in fluid communication with said anchoring and packing means, first piston means in said enclosed space, and means between said body and first piston means for shifting said first piston means into said enclosed space to develop an actuating pressure as said body is moved toward its said displaced positions; and wherein said second hydraulic means includes second piston means in said enclosed space, and means releasably securing said second piston means to said body for movement thereby toward its said normal position in response to such pressure differentials.

12. The Well packer of claim 11 further including bypass means normally open to the exterior of said well packer for compensating for changes in the volume of said anchoring means and enclosed space whenever said body is in its said normal position, and means responsive to movement of said body toward its said displaced positions for closing said bypass means to seal said pressurechamber means.

References Cited UNITED STATES PATENTS 2,925,128 2/1960 Page 166-121 3,288,219 11/1966 Young et al. 166-120 3,305,022 2/1967 Kisling 166-122 3,338,308 8/1967 Elliston et al. 166-120 CHARLES E. OCONNELL, Primary Examiner. DAVID H. BROWN, Examiner. 

4. A WELL TOOL SIZED AND ADAPTED FOR RECEPTION IN A WELL BORE COMPRISING: FIRST AND SECOND TELESCOPING MEMBERS MOVABLE RELATIVE TO ONE ANOTHER BETWEEN SPACED POSITIONS; PRESSURE-RESPONSIVE ANCHOR MEANS ON SAID FIRST MEMBER AND ADAPTED FOR EXTENSION INTO ANCHORING ENGAGEMENT WITH A WALL IN A WELL BORE IN RESPONSE TO AN ACTUATING PRESSURE; PRESSURE-CHAMBER MEANS FLUIDLY COUPLED TO SAID ANCHOR MEANS AND INCLUDING A PISTON THEREIN BETWEEN SAID MEMBERS; BYPASS MEANS NORMALLY OPEN TO THE EXTERIOR OF SAID WELL TOOL FOR COMPENSATING FOR CHANGES IN THE VOLUME OF SAID ANCHOR AND PRESSURE-CHAMBER MEANS WHENEVER SAID SECOND MEMBER IS IN ONE OF ITS SAID POSITIONS; FIRST MEANS RESPONSIVE TO MOVEMENT OF SAID SECOND MEMBER TOWARD THE OTHER OF ITS SAID POSITIONS FOR CLOSING SAID BYPASS MEANS TO SEAL SAID PRESSURE-CHAMBER MEANS; AND SECOND MEANS RESPONSIVE TO MOVEMENT OF SAID SECOND MEMBER TOWARD ITS SAID OTHER POSITION FOR MOVING SAID PISTON TO DEVELOP AN ACTUATING PRESSURE IN SAID PRESSURECHAMBER MEANS AFTER SAID BYPASS MEANS IS CLOSED. 